I just put together a very basic form with 5 required fields. Sent the embed code to a vendor and they've added to a microsite they built. 27 people have filled out the form -- 27 new lead records created in Marketo -- ALL BLANK.
The vendor implemented the form as a pop up / lightbox. I didn't give them lightbox embed code though.
Why do you think the fields are blank? I filled out the form myself, as a a test, and it comes through blank. Never had this happen before, and this form is the same config as every other one we've implemented.